RESUMEN
Pathogen host shifts represent a major source of new infectious diseases. There are several examples of cross-genus host jumps that have caused catastrophic epidemics in animal and plant species worldwide. Cross-kingdom jumps are rare, and are often associated with nosocomial infections. Here we provide an example of human-mediated cross-kingdom jumping of Exserohilum rostratum isolated from a patient who had received a corticosteroid injection and died of fungal meningitis in a Florida hospital in 2012. The clinical isolate of E. rostratum was compared with two plant pathogenic isolates of E. rostratum and an isolate of the closely related genus Bipolaris in terms of morphology, phylogeny, and pathogenicity on one C3 grass, Gulf annual rye grass (Lolium multiflorum), and two C4 grasses, Japanese stilt grass (Microstegium vimineum) and bahia grass (Paspalum notatum). Colony growth and color, as well as conidia shape and size were the same for the clinical and plant isolates of E. rostratum, while these characteristics differed slightly for the Bipolaris sp. isolate. The plant pathogenic and clinical isolates of E. rostratum were indistinguishable based on morphology and ITS and 28S rDNA sequence analysis. The clinical isolate was as pathogenic to all grass species tested as the plant pathogenic strains that were originally isolated from plant hosts. The clinical isolate induced more severe symptoms on stilt grass than on rye grass, while this was the reverse for the plant isolates of E. rostratum. The phylogenetic similarity between the clinical and plant-associated E. rostratum isolates and the ability of the clinical isolate to infect plants suggests that a plant pathogenic strain of E. rostratum contaminated the corticosteroid injection fluid and was able to cause systemic disease in the affected patient. This is the first proof that a clinical isolate of E. rostratum is also an effective plant pathogen.
Asunto(s)
Ascomicetos/fisiología , Plantas/microbiología , Animales , Ascomicetos/aislamiento & purificación , Ascomicetos/patogenicidad , Secuencia de Bases , ADN Intergénico/genética , Humanos , Funciones de Verosimilitud , Filogenia , Enfermedades de las Plantas/microbiología , Hojas de la Planta/microbiología , Poaceae/microbiología , Esporas Fúngicas/fisiologíaRESUMEN
A leaf spot and blighting were observed on leaves of tomato transplants from a producer in Florida in 2001 and 2002. A nonfluorescent bacterium was isolated consistently from affected tissue. The typical bacterium was a gram negative, strictly aerobic, slightly curved rod with one or two flagella. Sequence analysis of the 16S rRNA indicated that two representative strains, F1 and SE1, had greater than 99% nucleotide sequence identity with Herbaspirillum huttiense and H. rubrisubalbicans. The cellular fatty acid composition of the total of 16 tomato strains was very similar to H. huttiense and H. rubrisubalbicans. Based on carbon utilization, six of nine strains tested with the Biolog system were identified as Herbaspirillum spp. The tomato strains were oxidase positive and grew at 40°C, but were negative for levan production, pectate hydrolysis, and arginine dihydrolase activity. Based upon this polyphasic analysis, we concluded that the strains were most closely related to H. huttiense, although placement in this species would require further analyses. However, the tomato strains and H. rubrisubalbicans, but not H. huttiense, caused confluent necrosis when infiltrated at high concentrations into tomato leaves and were able to produce leaf spot symptoms on inoculated tomato seedlings in the greenhouse. Using pulsed-field gel electrophoresis, we determined that there was considerable variability between the strains collected in 2001 and 2002.